It certainly is still happening on both of my Lenovo W510 machines, and the slow down is really bad (I think Chrome is one of the best examples of how slow it gets, it's visible in Firefox but is not as bad). As others have noted, the bug has appeared in around Ubuntu's 2.6.32-26, as 2.6.32-25 did not exhibit the issue.

Update: Running kernel 2.6.38-9 now and I'm not experiencing the issue anymore (at least on Chrome).

I have been unable to find the time to build from a vanilla kernel, and that can be iffy anyway with all the distro-specific tweaks that get thrown in. Danix, have you tried reproducing this on Ubuntu with the kernel versions noted as problematic?